The present invention broadly relates to an article of furniture and, more specifically, pertains to a new and improved construction of an adjustable chair or seat structure.
Generally speaking, the chair of the present invention has a supporting framework on which a seat member and a back member are supported. The back member comprises a backrest portion and a strut portion. The seat member and the back member are coupled together by means of a pivot joint and are subject to the action of at least one spring element. The seat member and the back member can be adjusted to different angular positions. During the transition from one position to another, a relative motion is superimposed upon the pivoting or swivelling motion of the seat member and of the back member. It will be understood that the seat member and the back member are structural or frame members for supporting upholstery or panel members.
Chairs having both adjustable seats and adjustable back members are known in various forms. They allow the occupant to assume a working position on the one hand, in which the back member is nearly vertical and provides support for the back of the occupant, and a relaxing or reclined position on the other hand. Such chairs have a seat and a back member that are coupled together and angularly adjustable with respect to a supporting framework. The supporting framework is usually structured as a chair base upon which the seat and the back member are pivotably mounted.
The degree of comfort provided by such chairs is disturbed by the fact that in the transition to another seating position, especially in the transition from a working position to a relaxing or reclining position, the occupant is subjected to an undesirable stretching effect. This stretching effect can only be avoided by not using the backrest during the change of position.
In order to avoid this stretching effect, various solutions have been proposed. Among them is a construction disclosed in German Patent Publication No. 3,152,945 which is based upon a previously known construction having an angularly adjustable seat and an angularly adjusted back member coupled to the seat. In order to avoid the stretching effect, a supplementary linkage is provided which is connected to a back support portion that is perpendicularly slidable in relation to the back member. If the position of the chair is changed, the back support portion executes a supplementary motion relative to the back member. If the back upholstery is fastened to the back member, the desired avoidance of the stretching effect is obtained.
It should be obvious that this known construction constitutes a very complicated solution. In particular, the back support portion controlled by the supplementary linkage to be slidable in relation to the back member is a construction comprising a great many components which must be manufactured with an appropriate degree of accuracy.